Currently, there is a technology for controlling a plurality of storages. For example, there is a technology for providing a storage space used for reconstructing a storage disk array when a storage disk has failed. In addition, there is a technology for rearranging pieces of data distributed to a plurality of storages in an environment in which the plurality of storages exist. In addition, there is a technology that includes a first storage for which a high-speed, small-capacity storage apparatus is used and a second storage for which a low-speed, large-capacity storage apparatus is used. In addition, there is a technology for obtaining the variable period of access by continuously accumulating the number of times of access to data in unit time and for moving the data to a storage having appropriate performance among storage levels while referring to the obtained variable period (for example, refer to Japanese Laid-open Patent Publication No. 8-221876, Japanese Laid-open Patent Publication No. 2006-99748, Japanese Laid-open Patent Publication No. 2007-94946, and Japanese Laid-open Patent Publication No. 2003-216460).
However, in the above-described technologies in examples of the related art, there may be a plurality of candidates for a destination of data in a group of storages having three levels or more whose performance for response is different, and therefore it is difficult to move the data while determining a destination storage according to the access frequency, which changes depending on the access condition.